1. Field of the Invention
This invention relates to an output waveform control device for generating pulse waves by processing waveform data received from a CNC (Computer Numerical Control) unit and delivering the pulse waves, thereby causing a laser beam to be generated by pulsed oscillation. More particularly, this invention relates to an output waveform control device which is capable of generating a suitable laser beam by pulsed oscillation according to the type of machining, i.e. piercing, cutting, or welding.
2. Description of the Related Art
A laser beam used in a solid-state laser, such as a YAG laser, is excited by optical pumping through irradiation of a a luminous energy. The optical pumping is classified into a pulsed oscillation (in which pumping is effected in a pulsed manner) and continuous oscillation (in which pumping is continuously effected).
In the pulsed oscillation, the laser beam is generated based on the pulse waves input to a laser oscillator. The pulse waves, each of which is determined by an electric current value as a peak value of a pulse wave, a pulse duration, and a pulse repetition frequency, are delivered from an output control circuit incorporated in a power source block of the laser oscillator. The output control circuit modifies settings of the current value, the pulse duration, and the pulse repetition frequency, as determinants of the pulse waves, to thereby control the waveform of each pulse wave, which in turn controls the laser beam.
A pulse wave is formed of a predetermined number of (e.g. 20) pulse segments, each with pulse segment being set to an electric current value according to waveform data. Further, each pulse segment has a set pulse duration, and the whole duration (pulse wave duration) of one pulse wave is equal to the sum of the pulse durations of the segments. The pulse durations set to the pulse segments, respectively, are identical to each other and very short. That is, a very short duration is uniformly allocated to each pulse segment.
Thus, by allocation of a short duration to each pulse segment, the duration of each pulse wave is also short. For example, when the duration allocated to each pulse segment is equal to 0.1 msec, and the number of set pulse segments is equal to 20, the pulse wave duration is equal to 2 msec.
On the other hand, the pulse wave duration considered to be the optimum duration for piercing is short, and falls within a range of approximately 0.1 to 2.0 msec. Therefore, the pulse wave delivered from the output waveform control circuit has a shape suitable for piercing.
In contrast, in cutting and welding, a relatively long pulse wave duration is required, which falls within a range of approximately 1.0 to 10 msec. Therefore, the pulse wave delivered from the output control circuit is not necessarily suitable for cutting, or welding. To obtain a long pulse wave duration, however, since the pulse duration is uniformly allocated to each pulse segment, and the set number of pulse segments is limited, it has been impossible to increase the pulse duration.
As described above, conventional pulse wave duration control by the method of uniform allocation of an identical pulse duration to each pulse segment, can provide a laser beam suitable for piercing but cannot provide a laser beam suitable for cutting or welding. Moreover, although solid-state lasers conventionally have an application range mainly limited to piercing, there is a trend for a broadened application range of the solid-state laser. This broadend application range includes applications for cutting and welding, along with development of the technology related to the solid-state laser beam. From this point of view as well, pulse wave duration control adaptable to cutting and welding is demanded.